The present invention relates to a rotary vane compressor and, more particularly, to an improvement in the structure of suction port of such a compressor through which desired gas is sucked into a compression chamber.
As well known in the art, a rotary vane compressor comprises a casing made up of a cylinder and side blocks which are securely mounted on opposite ends of the cylinder. A rotor is disposed in the casing and formed with a plurality of substantially radially extending slots, or grooves, in which vanes are slidably nested. The casing, rotor and vane or vanes define a compression chamber whose volume is sequentially changed as the rotor and vanes are rotated. With the changing volume, the compression chamber sucks gas thereinto via a suction port and compresses the gas to feed it out forcing a delivery valve to open.
Concerning the structure, suction ports of rotary vane compressors heretofore proposed may generally be classified into two types, i.e., a sidewise type port which is formed through a side block to introduce gas sidewise into a compression chamber (e.g. Japanese Utility Model Laid-Open Publication No. 55-106392/1980), and a peripheral type port formed through a cylinder to introduce gas into a compression chamber in the peripheral direction (e.g. Japanese utility Model Laid-Open Publication No. 57-153792/1982). The sidewise type port has a charging efficiency which is high in a low speed range although low in a high speed range because no effect of inertia is available. The sidewise type port with such a characteristic is generally accepted more advantageous than the peripheral type for an automotive air conditioning system or the like which requires a high charging efficiency in a low speed range. To attain an additional charging efficiency with the side type suction port, the sectional area of the port opening into a compression chamber may be increased.
However, it is impossible to increase the sectional area of the sidewise type port and, therefore, the charging eficiency attainable with the sidewise type port beyond a certain limit. The width of the suction port available in the circumferential direction is limited by the positions of vanes. Where a suction port is formed simply by drilling a side block as in the prior art sidewise type port, the radial width of the port is limited by the configuration of the space between a cylinder and a rotor.